The invention relates generally to computed radiography, and more particularly, to correction of spatial luminance variation in computed radiography plates.
Typically, a computed radiography plate acts as a reusable X-ray image storage device. The computed radiography plate is initially exposed to X-ray radiation and placed into a reader for read-out and erasure. The plate is ready for a new X-ray exposure after erasure. During read-out of a computed radiography plate, an initial pixel array representing stored X-ray intensities over the plate must be corrected to account for various stationary, spatial variations in a structure of the plate and additional optical system variations. For example, the size of phosphor grains typically may be of a similar size as that of the pixel that leads to small variations in image intensity if uncorrected. Further, it is required to minimize structure noise to less than +/−0.1% of peak signal levels.
One of the commonly known correction techniques includes scanning a generic test plate exposed with a uniform X-ray radiation pattern and further using resultant array of values to produce a calibration image. The calibration image is used to compensate for large-scale grain noise and variation in optical transmission in a detection system. To achieve a highest signal-to-noise ratio in a range of greater than 200-300 to 1, detector elements need to be repositioned exactly each time a specific plate is read. Further, each detector pixel needs to be placed within a small fraction of a phosphor grain diameter.
However, it is not possible to passively mechanically align a plate relative to the detector elements to guarantee translation errors and rotational errors less than a desirable range due to large size and inherent flexibility of the plate. Moreover, most fixturing methods in use typically cause damage to a surface of the plate if improperly adjusted, thus limiting reuse of the plate.
Therefore, an improved system and method for correcting spatial luminance variation is desirable to address one or more of the aforementioned issues.